Anti-quorum sensing activity from marine bacteria

Unregulated consumption and overexploitation of antibiotics have paved the way for antibiotic-resistant strains and ‘superbugs’ emergence, posing a severe challenge in combating infectious diseases. Finding new effective antibiotic compounds is costly and time-consuming, and the possibility of developing resistance is high. In the last few decades, researchers have concluded that Quorum sensing (QS) genes firmly control the virulence artillery of the pathogen, and their expression drives the aggressiveness of the infection. Any organism's antibiotic resistance (AR) mechanism strengthens with the biofilm formation ability of microorganisms, which is mainly regulated by quorum sensing (QS). Quorum sensing (QS) is a global gene regulatory mechanism in bacterial pathogens expressing virulence factors by producing and secretion of small signalling molecules. QS is well studied at Pseudomonas aeruginosa. Turning off the QS system with an anti-infective agent is-a sustainable and potential strategy to tackle bacterial pathogens. QS inhibitors do not kill pathogens but disrupt their communication. Samples were collected from undisturbed areas along Gujarat’s coast of Gujarat like Mandvi, Dwarka and Diu. A total of 72 marine isolates were obtained, out of which 18 were associated with various marine macro-organisms like algae, whereas 54 were free living. The ability of quorum-sensing inhibition of all the isolates was tested against Serratia marcescens by co-culture technique to simultaneously detect signal-degrading and non-degrading quorum-sensing inhibitors. From primary co-culture screening total 44 bacterial isolates, including 12 macro-organism-associated bacteria and 32 living bacteria, were potentially found to have quorum sensing inhibitory potential against S. marcescens without affecting its growth. The present study describes the experimental results of selected isolates MB2 and DG5. Crude extract of both isolates was extracted with ethyl acetate to obtain the anti-QS compounds. Pigment inhibition in S. marcescens treated with crude extract was demonstrated by standard well diffusion assay and was found to have quorum sensing inhibitory activity without affecting its growth. Based on the above-obtained results, marine isolates were found to be a good candidate for the production of anti-quorum sensing molecules, which may serve as alternatives to conventional inhibitory molecules and can be a good candidate in future for the treatment of antimicrobial resistance disease.